叠前时间偏移技术在八宝矿区的应用

Application of Prestack Time Migration Technology in Babao Mine Area

八宝矿区总体构造形态为不对称的向斜构造,北翼岩层倾角达60°～80°,南翼倒转,矿区断层较多,三维地震叠后时间偏移成像困难,为此进行了三维叠前时间偏移外理。在本次地震资料处理中,选取偏移孔径为5000,依据CRP道集拉平程度确定叠前时间偏移速度场,以区内CMP道集内的炮检距分布情况确定最大、最小炮检距和炮检距增量,并将反假频距离确定为CMP间距的1～1.5倍。通过对比叠前、叠后时间偏移剖面,可以发现叠前时间偏移剖面能够较好地反眏深层构造及大倾角地层情况,其信噪比较高,地震剖面同相轴连续性好,断点清晰,处理效果显著。

Overall structural form of the Baobao mine area is an asymmetrical syncline, with strata dips in north limb up to 600-800, south limb overturned, and many faults. Imaging difficulties existed in 3D seismic poststaek time migration, thus 3D prestack time migration carried out. In this seismic data processing, migration aperture of 5000 has been selected, according to CRP trace gather flattened extent to determine prestack time migration velocity field. In virtue of offsets distribution within CMP trace gather determined maximum, minimum offsets and offset increments, and anti-aliasing distance as 1-1.5 times of CMP interval. Through contrast of prestack, poststack time migration sections, can find the former reflecting deep structures and large dip angle strata better, with higher S/N ratio, better seismic section lineup continuity, clearer breaking points, processing effects prominent.